As a new optical network architecture that can be built with currently available devices and can achieve bandwidth allocation with granularity finer than a wavelength, the light trail architecture attracts attention. For the light trail architecture using token passing medium access control, the split trail architecture is proposed. In the architecture, a trail is split into the upstream trail and the downstream trail at the token holding node and independent data transmissions on the two trails are permitted. As a result, we expect that the architecture achieves higher maximum throughput than the original unsplit trail architecture. The degree of throughput improvement by the split trail one depends on how appropriately we set upstream and downstream token holding times of each transmission node. In this paper, we formulate decision problem of the token holding times as a non-linear programming problem, derive the maximum throughput of the split trail architecture by solving the problem using NUOPT solver, and investigate the degree of improvement compared to the original one. According to numerical examples, the split trail architecture achieves 1) the same maximum throughput as the original one for its unfavorite traffic pattern where every transmission node sends data to the terminating node of the trail only, 2) about 1.6 times as high maximum throughput for an uniform traffic pattern where every node pair has the same sending rate, and 3) about 1.9 time as high maximum throughput for its favorite traffic pattern where every transmission node sends data to its adjacent downstream node only.
